Synthesis
GENERAL METHOD: Ethyl cyanoacetate (0.1 mol) was mixed with urea, methylurea and/or methylthiourea (0.1 mol) in anhydrous ethanol (290 mL) containing sodium. The reaction mixture was refluxed for 10-12 hours and subsequently cooled to room temperature. Acidification was carried out by adjusting the pH to 6 with acetic acid. The resulting precipitate was washed with distilled water and dried in a desiccator overnight.1a was obtained in 69% yield with a melting point over 360°C (literature value ≥ 360°C).
Purification Methods
Purify the aminouracil by dissolving it in 3M aqueous NH3, filtering hot, and adding 3M formic acid until precipitation is complete. Cool, filter off (or centrifuge), wash well with cold H2O, then EtOH and dry it in air. Dry it further in a vacuum at ~80o. [Barlin & Pfeiderer J Chem Soc (B) 1424 1971, Beilstein 25 III/IV 4107.]
References
[1] Russian Journal of Organic Chemistry, 2002, vol. 38, # 7, p. 1053 - 1055
[2] Journal of Chemical Research, 2016, vol. 40, # 12, p. 771 - 777
[3] Indian Journal of Chemistry - Section B Organic and Medicinal Chemistry, 1996, vol. 35, # 7, p. 662 - 668
[4] Australian Journal of Chemistry, 2007, vol. 60, # 2, p. 120 - 123
[5] Oriental Journal of Chemistry, 2010, vol. 26, # 4, p. 1281 - 1292
